Meijuan Huang

Impatiens walleriana is a widely cultivated ornamental species extensively used in landscaping and garden design, with its vibrant floral colors constituting one of the primary determinants of its ornamental value. We found in preliminary observations that treatment of I. walleriana seeds with colchicine at 60 mg L⁻¹ induced significant flower color variation, with petals changing from purple to pink. Based on this, the present study used the wild-type (purple) and induced mutant plants (pink) of I. walleriana as materials, and systematically elucidated the molecular regulatory mechanism underlying its flower color variation via integrated analysis of targeted metabolomics and transcriptomics. Metabolomic analysis identified 84 anthocyanin-related metabolites. Metabolite composition and accumulation levels differed significantly between Iw-MU and Iw-WT. Pelargonidin, peonidin, and petunidin were markedly elevated in Iw-MU, while procyanidins accumulated to higher levels in Iw-WT. These metabolic differences may serve as the key metabolic basis for the petal color transition to pink. Transcriptomic analysis identified a total of 689 differentially expressed genes, of which 386 were upregulated and 303 were downregulated. Subsequent functional annotation and enrichment analysis revealed that the flavonoid biosynthesis pathway played a key regulatory role in flower color variation. Among these, the significant downregulation of key anthocyanin biosynthetic genes, DFR and ANS, likely suppressed the production of colored anthocyanins. In contrast, the expression levels of ANR and LAR genes were significantly upregulated, which may drive the metabolic flux to shift toward proanthocyanidin biosynthesis. This study elucidated the metabolomic composition characteristics and key regulatory genes associated with the floral color transition from pinkish-purple to light pink in I. walleriana, as well as clarified the core metabolic pathways and molecular regulatory mechanisms underlying this variation. These findings provide a theoretical foundation for the genetic improvement of flower color and the breeding of new cultivars in I. walleriana.

Background: Petal variegation is an important ornamental trait in flowering plants and has major implications for both evolutionary biology, because it can promote speciation and diversity, and horticulture, because it enhances aesthetic appeal and commercial value. Here, we used Impatiens uliginosa as a model system and combined morphological, anatomical, physiological, biochemical, transcriptomic, and molecular approaches to investigate the mechanisms underlying petal variegation. Results: Freehand sectioning revealed that pigments were predominantly localized in the upper epidermal cells. Compared with the non-variegated dorsal petal regions, the variegated dorsal petal regions contained approximately three times as many pigment-accumulating cells; these cells were smaller, more densely arranged, and exhibited higher pigment density per unit area, collectively contributing to the darker coloration of the variegated regions. Pigment-content analysis showed that the variegated dorsal petal regions accumulated significantly higher levels of total carotenoids, anthocyanins, and flavonoids than the non-variegated dorsal petal regions. Semi-quantitative analysis further indicated that anthocyanin-related compounds, particularly delphinidin, pelargonidin, and peonidin derivatives, were enriched in the variegated dorsal petal regions. To investigate the molecular basis of this differential pigmentation, we performed comparative RNA-seq analysis of the variegated and non-variegated dorsal petal regions and identified a suite of candidate genes potentially involved in variegation formation. Functional validation of one candidate, IuMYB114 , was carried out using virus-induced gene silencing (VIGS). Silencing of IuMYB114 resulted in a significant reduction in both the size and color intensity of the variegated dorsal petal regions. qRT-PCR analysis confirmed that IuMYB114 expression in silenced plants was only 11% of that in wild-type plants. Moreover, the expression of several key anthocyanin-biosynthetic genes, including IuANS , IuUFGT , and IuF3′5'H , was significantly downregulated in the silenced lines. Conclusions: Taken together, these results suggest that IuMYB114 is likely associated with the positive regulation of anthocyanin biosynthesis and may play an important role in the formation of variegated and non-variegated dorsal petal regions in I. uliginosa , potentially through the regulation of anthocyanin biosynthetic genes. The spatially restricted expression of IuMYB114 may therefore contribute to differential anthocyanin deposition and, consequently, to petal variegation.

Impatiens morsei is an annual or perennial flower that is a member of the Impatiens genus in the Balsaminaceae family, with pink flowers and dark purple spots on the vexil and wing petals, which is important for the study of new flower colors of Balsaminaceae. However, there has been no study on the flavonoid biosynthesis pathway and carotenoid biosynthesis pathway of I. morsei and the mechanism of its pigment formation is still unclear. Transcriptome sequencing of spotted and non-spotted regions was performed using the petals of I. morsei at full bloom as test material. The results showed that (1) After transcriptome sequencing, 39,917 unigene sequences and 39,110 differentially expressed genes were obtained, and the number of genes that are down-expressed was higher than genes that are up-expressed. (2) Three key genes in the flavonoid biosynthetic pathway, FLS, PAL, and CHS1, were screened out. Additionally, two key genes in the carotenoid biosynthetic pathway, ABA1 and CCS, were identified. Furthermore, two regulatory genes, MSI4 and CPC, were also selected.and analyzed the spatiotemporal expression patterns of these seven genes. The results of this study lay a theoretical foundation for the study of the formation mechanism of floral spots in I. morsei.

Introduction: The genus Impatiens L. ( Balsaminaceae) is one of the three most important bedding plant genera globally, valued for its medicinal, ornamental, and economic properties. However, the morphological overlap among species and the lack of genomic data have limited our understanding of their molecular phylogenetic relationships. Methods: This study involved the sequencing of the chloroplast genomes of 9 Impatiens species, including Impatiens lateristachys, Impatiens siculifer var. porphyrea, Impatiens apalophylla, Impatiens pritzelii, Impatiens menghuochengensis, Impatiens membranifolia, Impatiens qingchengshanica, Impatiens aquatilis, and Impatiens racemosa. The study evaluated sequence divergence by comparing genomic features, repeat sequences, codon usage, IR expansion and contraction, sequence alignment, and selective pressures. It then constructed phylogenetic relationships using the maximum likelihood method, revealing the evolutionary relationships among these species. Results: The results indicated that the chloroplast genome sizes ranged from 151, 784 bp (I. racemosa) to 152, 628 bp (I. apalophylla), encoding between 108-115genes[77 to 81 protein-coding genes, 27 to 30 tRNA genes, and 4 rRNA genes]. Additionally, A detailed analysis was performed on the characteristics of repeat sequences, codon preferences, and IR region. Coding sections were more conserved than non-coding regions, and the IR regions were more conserved than the LSC and SSC regions, according to sequence variation and mutation hotspot analyses. The 9 species of Impatiens were classified into subgenus Clavicarpa and subgenus Impatiens, including the sections Impatiens and Racemosae, according to the phylogenetic tree. Discussion: This study presents the chloroplast genomes of 9 species within the genus Impatiens, marking a novel attempt at using phylogenetic analysis to determine the taxonomic positions of Impatiens species. It provides new molecular evidence for the systematic and evolutionary studies of Impatiens species.

Impatiens is a genus of functional herbaceous plants in the Balsaminaceae, which are not only of great ornamental value and one of the world’s top three flower bedding plants but also have a wide range of medicinal and edible uses. Currently, the taxonomy and phylogenetic relationships of Impatiens species are still controversial. In order to better understand their chloroplast properties and phylogenetic evolution, nine Impatiens plants (Impatiens repens, Impatiens rectirostrata, Impatiens baishaensis, Impatiens rostellata, Impatiens faberi, Impatiens oxyanthera, Impatiens tienchuanensis, Impatiens blepharosepala, Impatiens distracta) were sequenced, and their complete chloroplast genomes were analysed. Nine species of Impatiens chloroplast genomes ranged in length from 150,810 bp (I. rectirostrata) to 152,345 bp (I. blepharosepala). The chloroplast genomes were all typical circular DNA molecules, and the GC content in each region was consistent with the published chloroplast genomes of Impatiens plants. The results showed that the seven mutational hotspots (trnL-UAG, ndhG, ycf1, ccsA, rrn23, trnA-UGC, and ycf2) could be used as supporting data for further analyses of the phylogenetic tree and species identification. In addition, the results of the phylogenetic tree support that Balsaminaceae is a monophyletic taxon, and that Hydrocera triflora is at the base of the branch, is the original species of Balsaminaceae, and is in a sister group relationship with Impatiens species. The results of this paper enrich the data of Impatiens chloroplast genomes, and the availability of these chloroplast genomes will provide rich genetic information for species identification, thus enhancing the taxonomic accuracy and phylogenetic resolution of Impatiens, and further promoting the investigation and rational use of Impatiens plant resources.

One of the most important characteristics of ornamental plants is leaf color, which enhances the color of plant landscapes and attracts pollinators for reproduction. The leaves of Impatiens hawkeri ‘Sakimp005’ are initially green, then the middle part appears yellow, then gradually become white, while the edge remains green. In the study, leaves of I. hawkeri ‘Sakimp005’, in four developmental stages (S1-G, S2-C, S3-C, and S4-C), were selected for the determination of pigment content, chromaticity values, integrative metabolomics, and transcriptomics analyses. The carotenoid content of leaves varied significantly and regularly at four stages, and the colorimetric values corroborated the phenotypic observations. The results of integrative metabolomics and transcriptomics analysis show that the accumulation of two carotenoids (lutein and zeaxanthin), to different degrees in the leaves of I. hawkeri ‘Sakimp005’ at four stages, led to the vary yellowing phenomenon. We speculated that the carotenoid biosynthesis (containing two branches: α-branch and β-branch) in leaves by IhLUT1 and IhLUT5 in the α-branch and IhBCH2 genes in the β-branch differed. These findings provide a molecular basis for Impatiens plants’ leaf color breeding and improve the knowledge of the leaf color mechanism.

The genus Impatiens, which includes both annual and perennial herbs, holds considerable ornamental, economic, and medicinal value. However, it posed significant challenges for taxonomic and systematic reconstruction. This was largely attributed to its high intraspecific diversity and low interspecific variation in morphological characteristics. In this study, we sequenced samples from 12 Impatiens species native to China and assessed their phylogenetic resolution using the complete chloroplast genome, in conjunction with published samples of Impatiens. In addition, a comparative analysis of chloroplast genomes were conducted to explore the evolution of the chloroplast genome in Impatiens. The chloroplast genomes of 12 Impatiens species exhibited high similarity to previously published samples in terms of genome size, gene content, and sequence. The chloroplast genome of Impatiens exhibited a typical four-part structure, with lengths ranging from 146,987 bp(I. morsei)- 152,872 bp(I. jinpingensis). Our results identified 10 mutant hotspot regions (rps16, rps16-trnG, trnS-trnR, and rpoB-trnC) that could serve as effective molecular markers for phylogenetic analyses and species identification within the Impatiens. Phylogenetic analyses supported the classification of Impatiens as a monophyletic taxon. The identified affinities supported the taxonomic classification of the subgenus Clavicarpa within the Impatiens, with subgenus Clavicarpa being the first taxon to diverge. In phylogenetic tree,the Impatiens was divided into eight distinct clades. The results of ancestral trait reconstruction suggested that the ancestral traits of Impatiens included a perennial life cycle, four sepals and three pollen grooves. However, the ancestral morphology regarding fruit shape, flower colour, and spacing length remained ambiguous. Our study largely supported the family-level taxonomic treatment of Impatiens species in China and demonstrated the utility of whole chloroplast genome sequences for phylogenetic resolution. Comparative analysis of the chloroplast genomes of Impatiens facilitated the development of molecular markers.The results of ancestral trait reconstruction showed that the ancestor type of habit was perennial, the number of sepals was 4, and morphology and number of aperture was 3 colpus. The traits of capsule shape, flower colour, and spur length underwent a complex evolutionary process. Our results provided data support for further studies and some important new insights into the evolution of the Impatiens.

Flower color is a major feature of ornamental plants, and the rich flower color of plants is an important factor in determining their ornamental and economic values, so flower color is an important research target for gardening and horticulture breeders at home and abroad. Our research group collected four colors of Impatiens uliginosa (white, pink, red, and deep red) during the collection of germplasm resources in the field. In this study, we analyzed the transcriptomes of the four flower colors of I. uliginosa by using RNA-Seq technology. The transcriptomes were screened to identify candidate genes related to flower color, and the coloring mechanisms of four flower colors were revealed at the molecular level. The main findings were as follows: (1) The number of the four different transcripts ranged from 64,723 to 93,522 and contained a total of 100,705 unigenes. (2) The analysis of differentially expressed genes revealed structural genes including C4H, FLS, PAL, and ANS and transcription factors including MYB, MYB-related, AP2-EREBP, and bHLH. (3) Among the four flower colors of I. uliginosa, the C4H1 gene had the highest expression in pink flowers, and the C4H2 gene had the highest expression in red flowers. This indicated that C4H genes positively regulated the red flower color of I. uliginosa. However, FLS expression was the highest in white flowers, and with deepening flower color, FLS gene expression gradually weakened, acting as a negative regulator. The results of this study could lay the theoretical foundation for investigating the mechanism of coloration and flower color variation in I. uliginosa.